There are numerous different handle shapes for screwdrivers or similar tools. The earliest screwdrivers have a circular cross-section and an approximately convex longitudinal section. Apart from the circular cross-section, cross-sections are known, which are based on a subdivision into two or three. These include cross-sections in the form of a flattened circle and also triangular and hexagonal cross-sections. Polygonal cross-sections have been chosen to improve torque transmission.
A handle for hand tools is already known (DE 9202672), which has a pentagonal cross-section. The edges of the pentagonal cross-section are rounded and the arc length of the rounded part of the cross-section is everywhere substantially the same.
The problem of the invention is to provide an ergonomically improved handle for a screwdriver or similar tool with which it is also possible to transmit a torque. Tools of this type are e.g. screw clamps, where for clamping purposes a screwing movement must also be performed, together with ripping chisels, files, hacksaws,.etc., in which e.g. a twisting must be prevented, which means that a torque must also be applied, namely to prevent twisting.
To solve this problem the invention proposes a tool handle having a cross-section in the shape of a pentagon over a gripping part of its length, in which an orientation of the pentagon does not change over the length of the handle, and in which the cross-sectional shape has rounded corner sections, which are located on arcs having a center of curvature at the longitudinal axis of the handle, and in which the rounded corner sections of the cross-sectional shape are linked by substantially flat sides.
As a result of the cross-sectional shape in the form of a preferably rounded pentagon over a significant part of the handle length, the handle shape is better adapted to the human hand. Only in end regions gripped by a user for support purposes is there no pentagonal shape.
For reasons of symmetry, the invention prefers the cross-section in the form of an approximately regular pentagon. If symmetry is unnecessary, e.g. in the case of a hacksaw handle, an irregular pentagon can be used.
In a further development of the invention, the cross-sectional shape has rounded angle or corner sections, which are located on an arc with a centre positioned in the longitudinal axis of the handle. Thus, the pentagons are not completely formed and instead their sides are interconnected by rounded sections.
These sides of the approximate pentagonal shape can e.g. be slightly curved, with a much larger radius than the rounded angle sections. However, in particular the sides of the cross-sectional shape can be rectilinear.
In the parts of the tool handle, in which the cross-section is not shaped like an approximate pentagon, the cross-section is preferably circular. This is mainly a question of the rounded dome present at the free end of the handle. The user does not grasp at this point for torque transmission purposes and uses it only for supporting on the ball of the thumb or palm of the hand.
According to a further development of the invention a circular cross-section can also be provided on the opposite part of the tool handle, i.e. at the point where e.g. the screwdriver shank commences.
The shape of the tool handle can be represented by a rotationally symmetrical body with longitudinally directed flattenings.
According to a further development of the invention, the line linking the transition between the arcuate angle sections and the approximately rectilinear sides of the cross-sectional shape does not follow the longitudinal contour of the handle.
This can also be expressed in that the angle over which the arcuate section of the corners extends, is not the same at all points of the handle.
According to a further development of the invention, the tool handle has a first maximum cross-section point having a spacing of approximately 30% of the handle length from the handle dome end.
According to another further development of the invention, the tool handle can have a second maximum cross-section point, which has a spacing of approximately 60 to 70% of the handle length from the handle dome end.
The length of the handle is understood to mean the length available to the user for grasping purposes, i.e. extending from the dome end to a point where the user supports his thumb and optionally index finger.
According to a further development of the invention, the diameter of the tool handle at the first maximum cross-section point is approximately 15 to 18% larger than at the second maximum cross-section point. According to another further development of the invention, the approximately pentagonal shape of the cross-section of the tool handle terminates at the second maximum cross-section point and passes there into a circular cross-sectional shape. It has been found that at this point a circular shape is appropriate, because the ends of the index finger and thumb guide the tool.
According to a further development of the invention, the longitudinal profile of the tool handle from the second maximum cross-section point is concave and preferably up to the handle end associated with the tool. In this area the tool can either be rapidly turned or a finger support can be provided.
According to a further development of the invention, the smallest diameter of the handle is between the second maximum cross-section point and the handle end associated with the tool.
In particular, the maximum handle diameter is approximately 70 to 80% larger than the smallest handle diameter.